Lens-Based Vision Correction
High levels of short-sightedness or long-sightedness sit outside the range that some vision correction methods can safely treat, particularly where the cornea (the clear, dome-shaped surface at the front of the eye) is thinner than certain procedures require. Separately, from the mid-forties onwards, near vision often becomes noticeably harder to manage, as the eye’s natural lens gradually loses its ability to shift focus between distances, a change known as presbyopia (the natural, age-related loss of near focus).
ICL and Refractive Lens Exchange (RLE) are two procedures that address these two different situations. Rather than reshaping the cornea, both procedures use an implanted lens to correct vision. ICL adds a corrective lens while preserving the natural lens, whereas RLE removes and replaces the natural lens. Which of the two, if either, applies to a particular patient’s eyes depends on age, prescription and the physical structure of the eye itself.
ICL (Implantable Collamer Lens)
What Is ICL Used to Treat?
ICL is used to correct short-sightedness (myopia), or long-sightedness (hypermetropia), particularly at higher prescription levels than laser correction can safely treat. It may also be used, in some cases, to address astigmatism, a refractive error caused by differences in the shape of the cornea or lens that can produce blurred or distorted vision.
The ICL Procedure
A small incision, typically around 3mm, is made at the edge of the cornea. Through this incision, the surgeon inserts a foldable lens made of Collamer (a biocompatible, collagen-based material) into the posterior chamber, positioning it behind the iris (the coloured part of the eye) and in front of the eye’s own natural lens. Once in place, the lens unfolds and self-centres. Most current ICL models include a small central opening that allows fluid to flow naturally within the eye, removing the need for a separate procedure to manage eye pressure beforehand.
In Plain Terms: Rather than reshaping the cornea the way LASIK or PRK does, ICL adds a corrective lens inside the eye itself, positioned just in front of the eye’s own natural lens. The natural lens is left in place rather than removed, though because the two lenses sit close together, long-term monitoring of the space between them (the “vault”) is a normal part of post-operative care.
Who Is an Ideal Candidate for ICL?
Suitability is typically assessed in patients roughly 21 to 45 years old, with a prescription that has been stable for at least 12 months and no active eye disease. A key factor is whether there is enough space inside the eye, specifically between the cornea and the iris, to safely accommodate the lens; this is measured directly rather than assumed from age or prescription alone.
Recovery and Expected Results
Many patients notice improved vision within the first day, with most reaching stable results over the following couple of weeks. Because ICL is inserted inside the eye, follow-up appointments in the early recovery period specifically monitor eye pressure, which can take longer to settle in some patients than others. Where eye pressure needs closer monitoring or medication in the days after surgery, recovery extends accordingly; without that, most patients settle within the shorter timeframe described above.
Refractive Lens Exchange (RLE)
What Is RLE Used to Treat?
RLE corrects high levels of short-sightedness or long-sightedness or astigmatism and is also used to address presbyopia (the natural, age-related loss of near focus).
The RLE Procedure
RLE uses the same surgical technique as cataract surgery, phacoemulsification, but is performed on a clear lens rather than a clouded one. A small incision is made in the cornea, the eye’s natural lens is removed using ultrasonic energy, and an intraocular lens (IOL) is implanted in its place, selected according to the patient’s visual needs.
In Plain Terms: The eye’s own lens is removed entirely and replaced with an artificial one. It’s the same procedure used for cataracts, simply performed before a cataract has had the chance to develop.
Who Is an Ideal Candidate for RLE?
RLE is typically considered for patients from their mid-forties onwards, particularly once presbyopia has already reduced natural near focus, or where a prescription is too high for ICL or laser correction to safely treat. It is not generally recommended for younger patients whose eyes still have natural focusing ability worth preserving.
Recovery and Expected Results
Many patients notice improved vision within several days, although vision may take several weeks to stabilise. When a multifocal or extended depth-of-focus lens is selected, the brain typically needs a period of adjustment, known as neuroadaptation, to fully process the additional visual information those lenses provide; this can extend the time before vision feels completely settled, even once the eye itself has physically healed. With a standard single-focus lens, this extra adjustment period is not usually a factor.
ICL vs RLE: Which Might Apply?
ICL
ICL leaves the eye’s natural lens in place, which means the eye keeps its own natural ability to shift focus between distances. This is why it tends to suit younger patients who have not yet lost that ability to presbyopia.
RLE
RLE removes the natural lens entirely, which means that ability is given up as part of the procedure; this is generally only appropriate once age-related changes mean it would be lost regardless, or where the prescription falls outside the available ICL treatment range, or where the eye does not have sufficient anatomical space to accommodate an ICL safely.
Which of the two, if either, is appropriate depends on age, prescription and the physical dimensions of a patient’s own eye, assessed individually.
Potential Risks and Limitations
ICL and RLE are intraocular surgical procedures and involve potential risks. Depending on the procedure and the individual eye, these may include infection, inflammation, increased eye pressure, glare, haloes, undercorrection or overcorrection, retinal complications and the need for additional treatment or surgery. ICL-specific risks may include cataract formation, endothelial cell loss and the need to reposition, exchange or remove the lens. RLE-specific risks may include posterior capsule opacification. As RLE removes the natural lens, the ability to focus at different distances without correction is also lost as an expected outcome of the procedure, rather than as a complication. Rare complications may result in permanent loss of vision. The risks relevant to each patient are discussed during consultation and as part of the informed consent process.
Why an Accurate Assessment Matters
Performing RLE on a younger patient removes the eye’s natural focusing ability earlier than necessary, and unlike ICL, this is not reversible once the natural lens has been replaced. ICL, in turn, is not appropriate once early lens changes are already present, or where there is not enough space inside the eye to safely accommodate the implant; proceeding without confirming this can affect eye pressure and long-term eye health. Age, lens clarity and the precise internal dimensions of the eye therefore need to be assessed directly rather than inferred from prescription or age alone.
Dr David Robinson draws on more than 28 years of surgical experience when assessing patients for lens-based vision correction. During your consultation, he will assess which options are appropriate for your eyes, explain why one approach may be preferable to another, and discuss the potential benefits, limitations and expected visual outcomes. This gives you a clear understanding of why a particular treatment is being recommended and what you can reasonably expect from it before making a decision about surgery.
Common Questions Patients Ask
Can the ICL be removed later?
An ICL is intended to remain permanently in the eye, but it can be surgically removed or exchanged when clinically necessary. Removal requires another intraocular procedure with its own risks.
Does RLE mean cataract surgery will never be needed later?
Yes.Once the natural lens has been replaced with an artificial one, that artificial lens cannot itself develop a cataract, though the eye still requires normal, ongoing eye health monitoring afterwards.
Is either procedure painful?
Both procedures are generally performed under local anaesthetic. Patients may experience pressure or other sensations during surgery,but not sharp pain. Discomfort can occur during recovery.
How is it decided whether a patient needs ICL or RLE instead of laser surgery?
This comes down to prescription strength, corneal thickness, the physical space inside the eye and age-related lens changes, all of which are measured individually rather than inferred from a single factor.
Could a multifocal RLE lens cause issues with night vision?
The benefit of multifocal or extended depth-of-focus lenses is often distance and reading vision without glasses. The downside is sometimes glare or haloes around lights at night, particularly during the neuroadaptation period. This trade-off is discussed as part of lens selection, alongside the benefit of reduced glasses dependence, so the choice reflects a patient’s own priorities.